J/ApJ/783/119 z∼1 Lyα emitters. I. 135 candidates from GALEX (Wold+, 2014)
z∼1 Lyα emitters. I. The luminosity function.
Wold I.G.B., Barger A.J., Cowie L.L.
<Astrophys. J., 783, 119 (2014)>
=2014ApJ...783..119W 2014ApJ...783..119W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Photometry, ultraviolet ; Redshifts ;
Equivalent widths ; Active gal. nuclei ; X-ray sources
Keywords: cosmology: observations - galaxies: active -
galaxies: distances and redshifts - galaxies: evolution -
galaxies: starburst
Abstract:
We construct a flux-limited sample of 135 candidate z∼1 Lyα
emitters (LAEs) from Galaxy Evolution Explorer (GALEX) grism data
using a new data cube search method. These LAEs have luminosities
comparable to those at high redshifts and lie within a 7Gyr gap
present in existing LAE samples. We use archival and newly obtained
optical spectra to verify the UV redshifts of these LAEs. We use the
combination of the GALEX UV spectra, optical spectra, and X-ray
imaging data to estimate the active galactic nucleus (AGN) fraction
and its dependence on Lyα luminosity. We remove the AGNs and
compute the luminosity function (LF) from 60 z∼1 LAE galaxies. We find
that the best-fit LF implies a luminosity density increase by a factor
of ∼1.5 from z∼0.3 to z∼1 and ∼20 from z∼1 to z∼2. We find a z∼1
volumetric Lyα escape fraction of 0.7%±0.4%.
Description:
We construct a flux-limited sample of 135 candidate z∼1 Lyα
emitters (LAEs) from Galaxy Evolution Explorer (GALEX) grism data
using a new data cube search method. As described in Barger et al.
(2012ApJ...749..106B 2012ApJ...749..106B), we converted multiple GALEX NUV grism images
into a 3D (two spatial axes and one wavelength axis) data cube. Each
background subtracted data cube consists of thirty 20Å narrowband
slices covering a wavelength range of 2030-2630Å and a 50'*50'
field of view (FOV).
Spectroscopic observations were primarily obtained with the DEep
Imaging Multi-Object Spectrograph (DEIMOS) on Keck II in a series of
runs in 2012-2013. The observations were made with the ZD600 line/mm
grating blazed at 7500Å. This gives a resolution of ∼5Å with a
1'' slit and a wavelength coverage of 5300Å. We observed our
southern and equatorial fields (COSMOS and CDFS) with the Robert
Stobie Spectrograph on SALT from 2011 to 2013. The observations were
made with the pg1300 grating with the grating angle adjusted to ensure
spectral coverage of lines redward of [Ne V]. This gives a
resolution of ∼4Å with a 1.5" slit and a wavelength coverage of
2000Å.
In Tables 2-5, we list all of the LAE candidates in the Chandra Deep
Field-South (CDFS), GROTH, NGPDWS, and COSMOS fields ordered by
redshift.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 136 40 *Emission line sample: Chandra Deep Field-South
(CDFS)-00
table3.dat 136 41 *Emission line sample: GROTH-00
table4.dat 136 35 *Emission line sample: NGPDWS-00
table5.dat 136 19 *Emission line sample: COSMOS-00
--------------------------------------------------------------------------------
Note on table2.dat table3.dat table4.dat table5.dat:
The GALEX fields are defined by the following parameters from
Table1 in the paper:
----------------------------------------------------------------
Field name RA (J2000) DE Exp. Flux Nc LAE
(ks) (aW/m2)
----------------------------------------------------------------
CDFS 03:30:40 -27:27:43 353 1.8 40 24
GROTH 14:19:58 52:46:54 291 2.0 41 19
NGPDWS 14:36:37 35:10:17 165 2.3 35 11
COSMOS 10:00:29 +02:12:21 140 3.2 19 4
----------------------------------------------------------------
With "Flux"=flux threshold above which each field is greater
than 80% complete, "Nc"=number of LAE candidates, and
"LAE"=number of confirmed LAE galaxies.
--------------------------------------------------------------------------------
See also:
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
J/MNRAS/425/2116 : Arizona CDFS Environment Survey, ACES (Cooper+, 2012)
J/ApJ/744/110 : LAE galaxies between 2.1=<z≤3.1 (Ciardullo+, 2012)
J/ApJ/736/31 : HETDEX pilot survey. II. 1.9<z<3.8 LAEs (Blanc+, 2011)
J/ApJ/738/136 : LAEs between 0.19<z<1.25 with GALEX grism (Cowie+, 2011)
J/ApJ/725/394 : High-redshift Lyα emitters (Hu+, 2010)
J/ApJ/711/928 : Low-redshift Lyα galaxies from GALEX (Cowie+, 2010)
J/ApJS/191/124 : Optical spectroscopy of ECDF-S X-ray sources
(Silverman+, 2010)
J/ApJS/180/102 : AEGIS-X: Chandra deep survey (Laird+, 2009)
J/ApJ/696/1195 : COSMOS AGN spectroscopic survey. I. (Trump+, 2009)
J/ApJS/184/158 : Chandra COSMOS survey I. (Elvis+, 2009)
J/ApJ/693/1713 : Spectroscopy of X-ray sources in ECDF-S (Treister+, 2009)
J/A+A/498/13 : Lyman-α emitters from redshifts z∼2-3 (Nilsson+, 2009)
J/A+A/478/83 : GOODS-South Field VLT/FORS2 redshifts. III (Vanzella+, 2008)
J/ApJ/680/1072 : Lyα-emitting galaxies at 0.2<z<0.35 (Deharveng+, 2008)
J/ApJS/172/70 : zCOSMOS-bright catalog (Lilly+, 2007)
J/ApJ/671/1227 : Lyα galaxies at z∼4.5 (Dawson+, 2007)
J/ApJ/667/79 : Lyα emission-line galaxies at z=3.1 (Gronwall+, 2007)
J/ApJ/648/7 : Lyα emitters at z=6.5 in Subaru Deep Field
(Kashikawa+, 2006)
J/PASJ/58/313 : Lyα emitters in the SUBARU Deep Field
(Shimasaku+, 2006)
J/AJ/131/2373 : Extended Chandra Deep Field-South survey (Virani+, 2006)
J/ApJS/161/21 : Extended Chandra Deep Field-South survey (Lehmer+, 2005)
J/ApJS/161/9 : X-ray survey of the NDWFS Bootes field (Kenter+, 2005)
J/PASJ/57/165 : Lyα emitters in the SUBARU Deep Field
(Taniguchi+, 2005)
J/ApJS/155/271 : Chandra Deep Field-South: Optical spectroscopy
(Szokoly+, 2004)
J/AJ/126/539 : The Chandra Deep Fields North and South (Alexander+, 2003)
Byte-by-byte Description of file: table[2345].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [GALEX]
6- 18 A13 --- GALEX GALEX name (HHMMSS+DDMMSS; J2000)
20 A1 --- f_GALEX [i] Flag "i" on GALEX indicates LAE candidate
not listed in Barger et al.
(2012ApJ...749..106B 2012ApJ...749..106B)
22- 31 F10.6 deg RAdeg Right Ascension in decimal degrees based on
near-ultraviolet (NUV) position (J2000)
33- 43 F11.7 deg DEdeg Declination in decimal degrees based on
near-ultraviolet (NUV) position (J2000)
45- 49 F5.2 mag NUV [21.5/25.2] GALEX/NUV AB magnitude
51- 56 F6.2 mag FUV [-31.1/32.8] GALEX/FUV AB magnitude
58- 62 F5.3 --- zUV [0.67/1.17] Redshift from the GALEX
ultraviolet spectrum
64- 68 F5.2 [10-7W] LLya [42.2/43.7]? Logarithm of the Lyα
luminosity log L(Lyα) (in erg/s)
70- 72 I3 0.1nm EW [6/398]? Rest-frame Lyα equivalent
width EWr(Lyα) (in Å)
74- 75 I2 0.1nm e_EW [2/65]? The 1σ error in EW
77- 81 F5.1 [mW/m2] logFX [-15.4/-13.1]? Logarithm of the X-ray flux
(in erg/cm2/s) (1)
83 A1 --- f_logFX [e] Flag "e" on logFX indicates a source not
detected in X-ray (2)
85- 87 A3 --- UType Ultraviolet classified AGN
89- 98 F10.6 deg RA2deg ? Right Ascension in decimal degrees based
on optical position (J2000)
100-110 F11.7 deg DE2deg ? Declination in decimal degrees based on
optical position (J2000)
112-114 F3.1 arcsec Off [0.1/8.2]? Offset between the optical to
ultraviolet position
116-119 A4 --- n_zOpt Note on zOpt (no z=no optical redshift,
star, or *=optical redshift in brackets in
the paper)
121 A1 --- --- [(]
122-126 F5.3 --- zOpt [0.35/1.17]? Optical redshift zopt
127 A1 --- --- [)]
129-131 A3 --- f_zOpt Flag on zOpt (a-n) (3)
133-136 A4 --- OType Optical classification (AGN or star)
--------------------------------------------------------------------------------
Note (1): The X-ray fluxes are defined as below for the four fields:
CDFS-00 = log fa2-8keV (table 2);
GROTH-00 = log fa2-10keV (table 3);
NGPDWS-00 = log fa2-7keV (table 4);
COSMOS-00 = log fa2-10keV (table 5).
Note (2): e=Source not detected in X-ray hard band but detected in the soft
0.5-2keV flux band.
Note (3): Flag defined as follows:
a = X-ray data from Lehmer et al. 2005 (cat. J/ApJS/161/21);
b = This paper's DEep Imaging Multi-Object Spectrograph (DEIMOS) spectra;
c = This paper's SALT spectra;
d = Redshifts from Cooper et al. 2012 (cat. J/MNRAS/425/2116);
e = Treister et al. 2009 (cat. J/ApJ/693/1713 ) and Szokoly et al. 2004
(cat. J/ApJS/155/271 ) give z=0.977;
f = Silverman et al. 2010 (cat. J/ApJS/191/124);
g = [alt] Alternative counterpart at 52.942825, -27.494650, 2.2, (1.191)b
(R.A., Decl., Offset, zopt);
h = [alt] Two untargeted counterparts ∼2" from NUV position;
i = Archival DEIMOS DEEP2 spectra (Newman et al. 2013ApJS..208....5N 2013ApJS..208....5N);
j = [alt] Alternative counterpart at 215.05445, 52.667969, 4.4, no z
(R.A., Decl., Offset, zopt);
k = [alt] Alternative counterpart at 218.98737, 35.115852, 5.8, (1.096)b
(R.A., Decl., Offset, zopt);
l = [alt] Alternative counterpart at 218.79877, 35.394573, 4.0, (0.977)b
(R.A., Decl., Offset, zopt);
m = Archival Magellan spectra from Trump et al. 2009 (cat. J/ApJ/696/1195);
n = Archival VLT spectra from Lilly et al. 2007 (cat. J/ApJS/172/70).
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 03-Jun-2016